Broadband fishing sonar receiving beamforming method based on cylindrical transducer array

Abstract

The present invention provides a broadband fishing sonar receiving beamforming method based on a cylindrical transducer array, which is implemented using a cylindrical transducer array. In this method, a cylindrical transducer array is used to divide the detection area into multiple sectors, each sector corresponds to a partial arc array of a cylindrical transducer, and the entire horizontal 360° detection is achieved by performing horizontally uniformly spaced beam reception on each sector. Taking the device computing power into comprehensive consideration, multiple arrays are involved in a multi-channel receiver for processing, and the processing procedures of each multi-channel receiver are the same, thereby improving the maintainability of the system. The present invention adopts a broadband beamforming method based on a complex envelope, which reduces the system sampling rate requirements and achieves higher beamforming performance under lower sampling conditions.

Description

Technical Field

[0001] The present invention relates to the field of fishery equipment, and in particular to a broadband fishing sonar receiving beam forming method based on a cylindrical transducer array. Background Art

[0002] As the most typical marine fishing instrument, fishing sonar is an important means to obtain information on the quantity and spatial distribution of marine fish resources, and plays an important role in improving the efficiency, accuracy and selectivity of marine fishing. In order to obtain higher spatial detection resolution and fish species identification capabilities, marine fishery detection is rapidly developing in the direction of bandwidth, multi-beam and other technologies. In particular, with the development of microelectronics technology and artificial intelligence technology in recent years, the development of fishing sonar has brought new technical development directions. The continuous emergence of large-scale signal processors has provided hardware conditions for the use of more complex and higher-performance fish detection signal processing technology, thus bringing opportunities for the development of higher-performance fishing sonar.

[0003] Multi-beam fishing sonars usually use planar transducer arrays and cylindrical transducer arrays. Planar transducer arrays can only scan the sea area within a certain angle (generally less than 90°) of the fishing boat's heading; cylindrical transducer arrays can scan the horizontal 360° and vertical 60° centered on the fishing boat. Figure 1 As shown, the working process of the multi-beam fishing sonar is to first set a certain inclination angle according to the working environment, and then perform periodic repeated horizontal scanning. When a school of fish is found, a vertical scan is performed in the horizontal direction of the school of fish, thereby achieving multi-angle and three-dimensional detection of the school of fish.

[0004] Fishing sonars often use signals in the form of narrowband signals and broadband signals. Narrowband signal beamforming can be achieved through phase shifting, but its anti-reverberation ability, especially its ability to resist interface reverberation caused by sea surface and seabed reflections, is poor, which limits the detection distance of narrowband signal systems. Fishing sonars use broadband signals, which can effectively reduce the impact of interface reverberation and increase the detection distance of fishing sonars, but broadband signals have phase modulation, so they cannot be achieved through simple phase shifting. The traditional method sends multi-channel signals to the main control machine in a unified manner, and completes beamforming by delaying and accumulating them in the main control machine. This method has high requirements for the system sampling phase deviation and requires a higher sampling frequency. It also brings a large amount of calculations to subsequent signal processing, increases system complexity, and increases overall costs. Summary of the invention

[0005] In view of the defects in the prior art, the purpose of the present invention is to provide a broadband fishing sonar receiving beamforming method based on a cylindrical transducer array, which adopts a broadband beamforming method based on a complex envelope, reduces the system sampling rate requirement, and achieves higher beamforming performance under lower sampling conditions, thereby solving the complex problems of broadband signal fishing sonar systems in the prior art.

[0006] The technical solution provided by the present invention is:

[0007] A broadband fishing sonar receiving beamforming method based on a cylindrical transducer array is implemented by using a cylindrical transducer array, wherein the cylindrical transducer array includes a plurality of arrays distributed on a cylindrical surface, and the cylindrical transducer array is divided into a plurality of physical sectors along an axial direction; at least two adjacent physical sectors constitute a receiving sector for receiving beams, and the ratio of the arc length of the receiving sector to the circumference of the cylindrical transducer array is 1:3 to 1:6; at least one of the physical sectors participates in the beamforming process of at least two of the receiving sectors, and the receiving sector is used to simultaneously receive a plurality of beams, and the beamforming process of each beam includes the following steps:

[0008] (S1) calculating the acoustic path between each array in each receiving sector and the origin of the cylindrical transducer array;

[0009] (S2) sampling the signals received by each of the arrays;

[0010] (S3) obtaining the complex envelope of the sampled signal;

[0011] (S4) performing phase compensation on the complex envelope of the received signal of each of the arrays;

[0012] (S5) performing delay compensation on the phase-compensated complex envelope;

[0013] (S6) performing weighted accumulation on the delay-compensated complex envelopes of each array in each physical sector to form a partial beam;

[0014] (S7) Performing weighted addition on partial beams of each physical sector in the receiving sector to obtain an output beam.

[0015] A further improvement of the present invention is that the cylindrical transducer array includes 32 linear arrays distributed along the main line direction of the cylindrical surface; each linear array includes 8 arrays, and each linear array is evenly spaced on the cylindrical surface; each physical sector includes 4 linear arrays, and each receiving sector is composed of two physical sectors; the ratio of the arc length of the receiving sector to the circumference of the cylindrical transducer array is 1:4.

[0016] A further improvement of the present invention is that the signal received by the receiving array of each physical sector is processed by a multi-channel receiver. After obtaining the partial beam, the multi-channel receiver sends the partial beam to the main control machine, and the main control machine performs weighted addition on the partial beam to obtain the output beam.

[0017] A further improvement of the present invention is that, in the above step S1, the expression for calculating the acoustic path between the array i and the origin of the cylindrical transducer array is:

[0018]

[0019] Where: [x i ,y i , z i ] is the rectangular coordinate of element i in the cylindrical transducer array, is the incident direction of the beam to be received.

[0020] A further improvement of the present invention is that in step S2, the sampling frequency is 1Mhz, and the signal expression obtained by sampling is:

[0021] s i (n) = cos(2πf0n-2πf0τ i +γ(n-τ i ))+v i (n)

[0022] Where: f0 is the signal carrier frequency, γ(t) is the phase modulation function, v i (n) is the noise superimposed on the received signal, τ i The sound path difference.

[0023] A further improvement of the present invention is that in the above step S3:

[0024] The sampled signal s i (n) is multiplied by cos(2πf0n) and the result is low-pass filtered to obtain the real part of the complex envelope:

[0025] Xer i (t) = [cos(2πf0τ i +γ(n-τ i ))] / 2+w i (n)

[0026] The sampled signal s i (n) is multiplied by sin(2πf0n) and the result is low-pass filtered to obtain the imaginary part of the complex envelope:

[0027] Xim i (t) = [sin(2πf0τi +γ(n-τ i ))] / 2+w i (n)

[0028] Among them, w i (n) is the noise signal.

[0029] A further improvement of the present invention is that the complex envelope of the received signal of element i participates in the beamforming process of multiple beams received by the receiving sector where it is located.

[0030] A further improvement of the present invention is that in the above step S4: the complex envelope is subjected to a phase shift operation by a trigonometric function formula to remove the phase corresponding to Beam phase constant Its expression is:

[0031]

[0032] The above expression is expanded to get:

[0033]

[0034] A further improvement of the present invention is that, in the process of delay compensation in step S5, according to the array i for the direction The relative acoustic path difference of the beam The complex envelope is delayed and its expression is:

[0035]

[0036] For the array i, the direction is The complex envelope of the beam.

[0037] A further improvement of the present invention is that in the above step S6, each array in the physical sector is directed to The complex envelope of the beam is weighted, and its expression is:

[0038]

[0039] Among them, weight_total i is the weight in the weighted accumulation process, and its expression is:

[0040] weight_total=weight_line(:)*weight_column(1,:)

[0041] Among them, weight_line(:) is the weight of the i-th array in the vertical line array where it is located, and weight_column(1,:) is the weight of the line array where the array is located in the physical sector.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] (1) The fishing sonar of the present invention adopts a cylindrical transducer array to divide the detection area into multiple sectors. Each sector corresponds to a partial arc array of the cylindrical transducer. By receiving the horizontally uniformly spaced beams of each sector, the entire horizontal 360° detection is achieved. Taking the device computing power into comprehensive consideration, multiple arrays are involved in a multi-channel receiver for processing, so that each multi-channel receiver has the same processing program, thereby improving the maintainability of the system;

[0044] (2) The present invention adopts a broadband beamforming method based on a complex envelope, which reduces the system sampling rate requirement and achieves higher beamforming performance under lower sampling conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0046] Figure 1 It is a schematic diagram of the working process of multi-beam fishing sonar in the prior art;

[0047] Figure 2 This is a hardware architecture diagram of the omnidirectional broadband fishing sonar system used in the present invention;

[0048] Figure 3 Schematic diagram of the coordinate system of the cylindrical transducer array in this embodiment;

[0049] Figure 4 Schematic diagram of physical sector division of the cylindrical transducer array in this embodiment;

[0050] Figure 5 is a schematic diagram of a receiving sector;

[0051] Figure 6 Schematic diagram of the beam combining process between two multi-channel receivers;

[0052] Figure 7 is a schematic diagram of the beamforming process;

[0053] Figure 8 This is the waveform diagram of 20kHz-30kHz linear frequency modulation signal;

[0054] Fig. 9 It is a waveform diagram of the real part of the complex envelope of multiple phases;

[0055] Fig.10 The waveform diagram of the complex envelope of the three arrays after phase compensation;

[0056] Fig.11 It is the waveform diagram of the complex envelope after phase compensation;

[0057] Fig.12 The weighted accumulation output results of multiple arrays of a single multi-channel receiver;

[0058] Fig.13 The receiving sector performs beamforming on a certain receiving beam and finally outputs the result. DETAILED DESCRIPTION

[0059] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0060] The present invention provides a broadband fishing sonar receiving beam forming method based on a cylindrical transducer array. Figure 2 The omnidirectional broadband fishing sonar system shown in the figure is implemented. The omnidirectional broadband fishing sonar includes a 256-channel cylindrical transducer array, a signal processing host and a main control machine.

[0061] In the cylindrical transducer array, each array is distributed on the cylindrical surface of the cylindrical transducer array, and each array works independently to complete the electroacoustic conversion when transmitting the underwater acoustic signal and the acoustic-electric conversion when receiving it.

[0062] The signal processing host is composed of several multi-channel receivers (for multi-channel reception and transmission, signal processors, transceiver switches, etc.), switches, backplanes, etc. It is responsible for generating transmission signals and driving the transmission circuit during transmission to achieve high-power signal transmission; when receiving, it performs analog and digital processing on the signals received by the transducer array, including filtering, amplification, down-conversion, beamforming, etc.

[0063] The main control machine is responsible for the entire sonar operating parameter setting, operating mode setting and other host control processes as well as the acoustic echo image processing process; other peripheral modules include display, keyboard (including mouse) and signal processing host are used together to complete the display of sonar detection images and the input and control of setting parameters.

[0064] In order to simultaneously transmit and receive multiple beams, the array of the cylindrical transducer array in the present invention adopts a multiplexing design according to sectors. Each array is distributed on the cylindrical surface, and the axis of the cylindrical surface is arranged in the vertical direction when in use. The sector is divided into multiple physical sectors according to the transducer along its axis direction, and each physical sector includes a plurality of arrays distributed on the arc-shaped sector surface.

[0065] There is no unique way to divide physical sectors. For example, a physical sector with a smaller arc length can be used in the key detection direction and a denser array can be installed, while a sector with a larger arc length can be used in the non-key direction and the array can be arranged more sparsely. Physical sectors can also be divided in the form of equally divided cylindrical surfaces, for example, a cylindrical transducer array can be equally divided into 12 physical sectors (each with an arc of 30°), 8 physical sectors (each with an arc of 45°), and 6 physical sectors (each with an arc of 60°) along its axis.

[0066] In a cylindrical transducer array, at least two adjacent physical sectors constitute a receiving sector for receiving a beam. Each receiving sector is used to receive multiple waveforms. Each physical sector participates in at least two receiving sectors, thereby realizing a multiplexing design. In view of the above-mentioned multiple physical sector division methods, the receiving sectors may also adopt multiple corresponding division methods. For example, for a cylindrical transducer array divided into 12 physical sectors, any 2 or 3 adjacent physical sectors may be divided into a receiving sector, in which case the ratio of the arc length of the physical sector to the circumference of the cylindrical transducer array is 1:6 or 1:4. For a cylindrical transducer array divided into 6 physical sectors, any 2 adjacent physical sectors may be divided into a receiving sector, in which case the ratio of the arc length of the physical sector to the circumference of the cylindrical transducer array is 1:3.

[0067] like Figure 3 , 4 As shown in FIG. 1 , in a specific embodiment, the cylindrical transducer array is evenly divided into 8 physical sectors along its axis, each physical sector has an arc length of 45°, and each physical sector has 32 arrays. In the signal processing host, the signals received by the arrays of each physical sector are processed by a 32-channel receiver / transmitter (hereinafter referred to as a multi-channel receiver). In each physical sector, the 32 arrays are divided into four columns, and each column of arrays is parallel to the axis of the cylindrical transducer array.

[0068] In order to facilitate signal processing, a coordinate system needs to be established in the cylindrical transducer array so as to clarify the coordinate position of each array. In the above embodiment, the origin of the transducer coordinate system is the center of the transducer. The ship's navigation direction is the X-axis direction, the horizontal and vertical direction of the heading direction is the Y-axis direction, and the vertical direction of the heading direction is the Z-axis direction. The origin of the Z-axis is at the middle of the transducer height.

[0069] In the above embodiment, the cylindrical transducer array has M rows and N columns, M is 8, and N is 32. A column is an array arranged in a straight line, forming a line array. The line array is arranged along the busbar direction of the cylindrical transducer array, and each line array is distributed at equal intervals on the cylindrical surface.

[0070] The adjacent linear arrays are staggered in the vertical direction. The vertical staggered distribution means that, in any three adjacent linear arrays, the linear arrays on both sides are at the same height, while the linear array in the middle is higher or lower than the other two linear arrays. In the cylindrical transducer array, a row of arrays forms a circle in which two adjacent arrays are staggered up and down. The column numbers are numbered counterclockwise from the right side of the X-axis as 1, 2, 3...31, 32. The row numbers are 1, 2, 3...7, 8 from bottom to top. Corresponding to the spherical coordinate system, from the X-axis, it is 0 to 180° counterclockwise, and 0 to -180° clockwise. The vertical direction Z-axis positive semi-axis is -90° to 90° from top to bottom. Such as Figure 4 As shown, eight multi-channel receivers numbered 1# to 8# are respectively responsible for receiving signals from each array in a physical sector.

[0071] like Figure 4 , 5 As shown, the cylindrical transducer array has a total of 8 receiving sectors. Among them, the physical sectors corresponding to multi-channel receiver 8# and multi-channel receiver 1# constitute the first receiving sector; the physical sectors corresponding to multi-channel receiver 1# and multi-channel receiver 2# constitute the second receiving sector; the physical sectors corresponding to multi-channel receiver 2# and multi-channel receiver 3# constitute the third receiving sector; and so on. The eight physical sectors constitute a total of eight receiving sectors with an arc length of 90°, and each physical sector has an arc length of 45°, participating in two receiving sectors.

[0072] For each receiving sector, its independent coordinate system needs to be determined, and each receiving sector includes a coordinate system in the same form. For a receiving sector, the independent coordinate system uses the coordinate origin of the cylindrical transducer array as the coordinate origin of the receiving sector, the normal of the sector arc passing through the origin as the X-axis, the horizontal vertical line passing through the origin as the Y-axis, and the Z-axis of the cylindrical array as the Z-axis. The vertical angle definition in the spherical coordinate system is consistent with that of the cylindrical transducer array, and the horizontal angle definition is defined by its own X-axis, from the X-axis counterclockwise 0 to 180°, and clockwise 0 to 180°. That is, the horizontal angle of the sector is the horizontal angle in the coordinate system of the cylindrical transducer array minus the sector rotation angle.

[0073] In the above embodiment, the cylindrical transducer array has 8 receiving sectors, each receiving sector completes 20 beams, covering the area from -22.5° to 22.5° in front of each receiving sector (in the independent coordinate system of the receiving sector), and the beam spacing is 2.25°. The horizontal angles of the 20 beams for each receiving sector are: -21.375°, -19.125°, -16.875°, -14.625°, -12.375°, -10.125°, -7.875°, -5.625°, -3.375°, -1.125°, 1.125°, 3.375°, 5.625°, 7.875°, 10.125°, 12.375°, 14.625°, 16.875°, 19.125°, 21.375°.

[0074] like Figure 4 , 5 As shown, in the above embodiment, since there is a common physical sector between the two receiving sectors, the multi-channel receiver corresponding to the single physical sector needs to participate in the forming of 40 beams; for the multi-channel receiver of the single physical sector, the left half beam or the right half beam of a beam it participates in receiving can be obtained through the arrays connected to it. After obtaining the left / right half beam, the multi-channel receiver sends it to the main control machine through the switch, and the main control machine can perform weighted superposition on the left half beam and the right half beam of each beam it receives to obtain each output beam.

[0075] like Figure 6 , 7 As shown, specifically, the forming process of each beam includes the following steps:

[0076] (S1) Calculate the acoustic path between each array in the receiving sector and the origin of the cylindrical transducer array; the calculation process is performed in an independent coordinate system of the receiving sector; assume that the rectangular coordinates of the array in this coordinate system are [x i ,y i , z i ], then the expression of the acoustic path between array i and the origin of the cylindrical transducer array is:

[0077]

[0078] in, is the incident direction of the beam to be received; for different beams to be received, there are different acoustic path differences between array i and the origin of the coordinate system.

[0079] (S2) Sampling the signals received by each array; when the multi-channel receivers are synchronized, the underwater acoustic echo signal is digitally sampled using a sampling frequency of 1 MHz, and the broadband signal to be received is:

[0080] s(t)=cos(2πf0t+γ(t))

[0081] Where f0 is the signal carrier frequency and γ(t) is the phase modulation function. Figure 8 The linear frequency modulation signal with a carrier frequency of 20kHz and a bandwidth of 10kHz in this embodiment is shown.

[0082] For any signal received by array i, there is a certain delay τ due to the sound path difference. i The delay is related to the beam direction. At the same time, the received signal is superimposed with noise v i (n). Then the expression of the received signal of array i is:

[0083] s i (n) = cos(2πf0n-2πf0τ i +γ(n-τ i ))+v i (n)

[0084] Where: f0 is the signal carrier frequency, γ(t) is the phase modulation function, v i (n) is the noise superimposed on the received signal, τ i is the sound path difference. Expanding the above formula, we can get

[0085] s i (n) = cos(2πf0n-2πf0τ i +γ(n-τ i ))+v i (n)

[0086] Since the carrier frequency does not contain useful signal information, beamforming can be performed by obtaining the phase modulation function θ(n) to improve the system output signal-to-noise ratio.

[0087] To make it easier for everyone to understand, the following is an explanation of the process of simple trigonometric function operations. In the above formula, 2πf0n, -2πf0τ i , -τ i There are three characteristic quantities, of which the last two are related to a given array and a given beam direction. We need to remove these three quantities through signal processing to obtain the complex envelope cos(θ(n)) of the received signal of each array. Finally, we sum the complex envelopes of the received signals of all arrays in the sector to obtain the beamforming result. In the next step, we will remove 2πf0n by down-conversion + low-pass filtering, and remove -2πf0τ by phase shifting. i , and remove -τ by delay i .

[0088] (S3) Obtaining the complex envelope of the sampled signal; by obtaining the complex envelope, the carrier frequency that does not contain useful information can be removed. Using the envelope signal for beamforming can reduce the phase error effect of the sampled signal. Specifically, obtaining the complex envelope specifically includes the following steps:

[0089] (S31) The sampled signal s i (n) is multiplied by cos(2πf0n) and the result is low-pass filtered to obtain the real part of the complex envelope: Xer i (t) = [cos(2πf0τ i +γ(n-τ i ))] / 2+w i (n).

[0090] The sampled signal s i The expression after multiplying (n) by cos(2πf0n) is:

[0091] s i (n).*cos(2πf0n)=cos(2πf0n-2πf0τ i +γ(n-τ i )).*cos(2πf0n)+v i (n)*cos(2πf0n)

[0092] According to the trigonometric function formula, the above formula can be obtained as follows:

[0093] =[cos(2πf0τ i +γ(n-τ i ))+cos(2π*2f0n-2πf0τ i +γ(n-τ i ))] / 2+v i (n)*cos(2πf0n)

[0094] Low-pass filtering can obtain the real part of the complex envelope of the signal

[0095] Xer i (t) = [cos(2πf0τ i +γ(n-τ i ))] / 2+w i (n)

[0096] (S32) The sampled signal s i (n) is multiplied by sin(2πf0n) and the result is low-pass filtered to obtain the imaginary part of the complex envelope:

[0097] Xim i (t) = [sin(2πf0τ i +γ(n-τi ))] / 2+w i (n)

[0098] Among them, w i (n) is the noise signal.

[0099] The complex envelope obtained in this step includes information about all beams that array i needs to receive, so the complex envelope of array i obtained in step (S3) needs to participate in multiple beamforming processes. In the process of forming multiple beams in a certain receiving sector, the complex envelope of each array in the receiving sector only needs to be obtained once. Fig. 9 Shown is a waveform diagram of the real part of the complex envelope of multiple arrays.

[0100] (S4) performing phase compensation on the complex envelope of the received signal of each of the arrays. The real part Xer of the complex envelope i (n) and the imaginary part Xim i (n) The expression includes variables The corresponding direction for each array is The phase constant of the beam is removed by performing phase shift operation using trigonometric formulas; its expression is:

[0101]

[0102] The above expression is expanded to get:

[0103]

[0104] Fig.10 The waveform diagram of the complex envelope of the three arrays after phase compensation. After phase compensation, for any receiving beam, the receiving signals of each array only differ by a fixed time delay.

[0105] (S5) Delay compensation is performed on the complex envelope after phase compensation. The purpose of delay compensation is to eliminate the above-mentioned fixed delay. In the delay compensation process, according to the array i for the direction The relative acoustic path difference of the beam The complex envelope is delayed and its expression is:

[0106]

[0107] For the array i, the direction is The complex envelope of the beam. Fig.11 It can be seen that after compensation, for any receiving beam, the receiving signals of each array are almost overlapped.

[0108] (S6) performing weighted accumulation on the complex envelopes of each array in each physical sector after delay compensation to form a partial beam; for any receiving beam, the two physical sectors perform weighted accumulation on the complex envelopes to obtain a left half beam and a right half beam respectively.

[0109] In this embodiment, the expression for the weighted accumulation process of the complex envelope of each array in a physical sector of a certain receiving beam is:

[0110]

[0111] Among them, weight_total i is the weight in the weighted accumulation process, and its expression is:

[0112] weight_total=weight_line(:)*weight_column(1,:)

[0113] Among them, weight_line(:) is the weight of the i-th array in the vertical line array where it is located, and weight_column(1,:) is the weight of the line array where the array is located in the physical sector.

[0114] The above weighted accumulation process can be understood as a joint weighting of a linear array and a circular arc. The above process can suppress side lobes and obtain better beamforming directivity. The same phase modulated signal can be obtained through step S5, but in practice, due to the influence of noise, the signal has differences. By utilizing the incoherent characteristics of noise, multi-array signal accumulation can also cancel out the noise part, and at the same time, the received signal can be enhanced by weighting to obtain better directivity gain.

[0115] In the above process, the complex envelope of each array includes the signals of multiple beams to be received, but after phase compensation and delay compensation are performed on a specific beam to be received, the signal phase of the specific beam to be received in the complex envelope of each array is consistent, while the phases of other beams are randomly distributed, similar to noise. Therefore, in the above weighted accumulation process, the amplitude of the specific beam to be received with consistent phase is highlighted, while the beams of other signals are offset in the weighted accumulation process due to the random distribution of phase. Therefore, in this embodiment, a specific beam to be received is extracted from multiple beams to be received by performing phase compensation and delay compensation on the specific beam to be received.

[0116] from Fig.12 It can be seen that for a certain receiving beam, the amplitude of the signal increases significantly after the complex envelopes of each array in a single physical sector are accumulated.

[0117] (S7) performing weighted addition on the partial beams of each physical sector in the receiving sector to obtain an output beam. In this embodiment, a receiving sector includes two physical sectors. After the multi-channel receiver corresponding to the physical sector obtains the partial beam, it sends the partial beam to the main control machine through the switch, and performs weighted addition on the partial beams of each receiving beam in the main control machine to obtain the signal of each receiving beam. Its expression is:

[0118]

[0119] Fig.13 The figure shows the signal waveform after weighted addition of each partial beam of a receiving beam. In this embodiment, each multi-channel receiver generates a partial beam independently, avoiding the transmission of the receiving signal of each beam to the main control machine. This distributed processing method can make full use of the computing resources of the system and reduce the communication bandwidth of the system.

[0120] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0121] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A broadband fishing sonar receiving beamforming method based on a cylindrical transducer array, which is implemented by using a cylindrical transducer array, wherein the cylindrical transducer array includes a plurality of arrays distributed on a cylindrical surface, and the cylindrical transducer array is divided into a plurality of physical sectors along an axial direction; at least two adjacent physical sectors constitute a receiving sector for receiving a beam, and the ratio of the arc length of the receiving sector to the circumference of the cylindrical transducer array is 1:3 to 1:6; at least one of the physical sectors participates in the beamforming process of at least two of the receiving sectors, and the receiving sector is used to simultaneously receive a plurality of beams, and the beamforming process of each beam includes the following steps: (S1) calculating the acoustic path between each array and the origin of the cylindrical transducer array; (S2) sampling the signals received by each of the arrays; (S3) obtaining the complex envelope of the sampled signal; (S4) performing phase compensation on the complex envelope of the received signal of each of the arrays; (S5) performing delay compensation on the phase-compensated complex envelope; (S6) performing weighted accumulation on the delay-compensated complex envelopes of each array in each physical sector to form a partial beam; (S7) performing weighted addition on partial beams of each physical sector in the receiving sector to obtain an output beam; In the above step S1, the expression for calculating the acoustic path between the array i and the origin of the cylindrical transducer array is: Where: i ,y i , z i ] is the rectangular coordinate of element i in the cylindrical transducer array, θ j , is the incident direction of the beam to be received; In step S2, the sampling frequency is 1Mhz, and the signal expression obtained by sampling is: s i (n)=cos(2πf0n-2πf0τ i +γ(n-τ i ))+v i (n) Where: f0 is the signal carrier frequency, γ(t) is the phase modulation function, v i (n) is the noise superimposed on the received signal, τ i is the sound path difference; In the above step S3: The sampled signal s i (n) is multiplied by cos(2πf0n) and the result is low-pass filtered to obtain the real part of the complex envelope: Xer i (t)=[cos(2πf0τ i +γ(n-τ i ))] / 2+w i (n) The sampled signal s i (n) is multiplied by sin(2πf0n) and the result is low-pass filtered to obtain the imaginary part of the complex envelope: Xim i (t)=[sin(2πf0τ i +γ(n-τ i ))] / 2+w i (n) Among them, w i (n) is the noise signal; The complex envelope is phase-shifted by trigonometric formula to remove the corresponding direction θ j, Beam phase constant Its expression is: The above expression is expanded to get: In the process of delay compensation in step S5, according to the array i for the direction θ j, The relative acoustic path difference of the beam The complex envelope is delayed and its expression is: For array i, the direction is θ j, The complex envelope of the beam.

2. A broadband fishing sonar receiving beamforming method based on a cylindrical transducer array according to claim 1, characterized in that: The cylindrical transducer array includes 32 linear arrays distributed along the main line direction of the cylindrical surface; each linear array includes 8 arrays, and the linear arrays are evenly spaced on the cylindrical surface; each physical sector includes 4 linear arrays, and each receiving sector includes two physical sectors; the ratio of the arc length of the receiving sector to the circumference of the cylindrical transducer array is 1:

4.

3. A broadband fishing sonar receiving beamforming method based on a cylindrical transducer array according to claim 2, characterized in that: The signal received by the receiving array of each physical sector is processed by a multi-channel receiver. After obtaining the partial beam, the multi-channel receiver sends the partial beam to the main control machine, and the main control machine performs weighted addition on the partial beam to obtain the output beam.

4. The broadband fishing sonar receiving beamforming method based on a cylindrical transducer array according to claim 1 is characterized in that: The complex envelope of the received signal of element i participates in the beamforming process of multiple beams received by the receiving sector where it is located.

5. The broadband fishing sonar receiving beamforming method based on a cylindrical transducer array according to claim 1 is characterized in that: In the above step S6, each array in the physical sector is directed to θ j, The complex envelope of the beam is weighted, and its expression is: Among them, weight_total i is the weight in the weighted accumulation process, and its expression is: weight_total=weight_line(:)*weight_column(1,:) Among them, weight_line(:) is the weight of the i-th array in the vertical line array where it is located, and weight_column(1,:) is the weight of the line array where the array is located in the physical sector.

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